M85.48 identifies a solitary bone cyst occurring at an anatomical site not captured by any other specific M85.4x subcode — a true 'other site' residual category within the solitary bone cyst family.
Verified May 8, 2026 · 3 sources ↓
- Status
- Billable
- Chapter
- 13
- Related CPT
- 6
- Region
- Other
Documentation tips
What should appear in the chart to support M85.48.
Source · Editorial brief grounded in 3 cited references ↓
- Identify the exact bone affected by name in the clinical note — 'solitary bone cyst, left ilium' or 'unicameral cyst, posterior rib' is auditable; 'bone cyst, other site' without a named bone is not.
- Record imaging modality and key findings (e.g., central lytic lesion, sclerotic margins, fluid signal on MRI T2) to support medical necessity for any associated imaging CPT codes.
- If a pathological fracture through the cyst wall is present, document that relationship explicitly so coders can sequence M84.58xA as the principal diagnosis with M85.48 as secondary.
- Note whether the cyst is incidental or symptomatic; symptomatic lesions requiring aspiration or corticosteroid injection need operative or procedural documentation tied to this diagnosis.
- Confirm the site does not fall under a named M85.4x subcode (shoulder, forearm, hand, thigh, lower leg, ankle/foot) before assigning M85.48 — mismatch is a common audit flag.
Related CPT procedures
Procedure codes commonly billed with M85.48. Linking the right diagnosis to the right procedure is what establishes medical necessity.
Source · CMS LCDs · AAOS specialty guidance · claims-pattern analysis
Common coding pitfalls
The recurring mistakes coders make with M85.48 and adjacent codes.
Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓
- Assigning M85.48 when a site-specific M85.4x subcode exists — always check the full M85.4 subcode list before defaulting to 'other site.'
- Using M85.48 as the principal diagnosis when a pathological fracture through the cyst is documented — the fracture code (M84.58xA/D/S) should lead.
- Confusing solitary bone cyst (M85.4x) with solitary cyst of the jaw, which is explicitly excluded and maps to M27.4 — the Excludes2 note at the M85.4 level requires a separate code if both conditions exist.
- Omitting a second code for osteogenesis imperfecta (Q78.0), osteopetrosis (Q78.2), or polyostotic fibrous dysplasia (Q78.1) when those conditions coexist — all carry Excludes1 restrictions at the M85 level, meaning they cannot be coded alongside M85.48.
- Leaving the anatomical site undocumented and assuming 'other site' covers any unspecified location — M85.48 requires a named but unlisted site, not a missing site.
Clinical context
Source · Editorial summary grounded in 3 cited references ↓
M85.48 is the correct code when a solitary (simple/unicameral) bone cyst is confirmed at a location that does not match the site-specific M85.4x subcodes already defined in the M85.4 family. Those named subcodes cover shoulder/upper arm, forearm, hand, thigh, lower leg, and ankle/foot. If the cyst sits in the pelvis, rib, sternum, clavicle, scapula, vertebra, skull, or any other named skeletal site outside those ranges, M85.48 is the appropriate billable code.
Solitary bone cysts are benign, fluid-filled intraosseous lesions most commonly encountered incidentally on imaging or following a pathological fracture through the cyst wall. Diagnosis is typically supported by plain radiography showing a central lytic lesion with a well-defined sclerotic margin, often confirmed by MRI or CT. When a pathological fracture through the cyst is present, code the fracture first (M84.58xA/D/S series) and add M85.48 as a secondary diagnosis — do not use M85.48 as the principal code in that scenario.
Because this is a true 'other site' residual bucket, documentation must name the specific bone involved. A note that says only 'solitary bone cyst' without identifying the anatomical location leaves the coder unable to confirm M85.48 is correct versus a more specific subcode. Imaging reports, surgical pathology, or operative notes that name the affected bone provide the specificity needed to defend this code on audit.
Sibling codes
Other billable codes under M85.4 (laterality / anatomic variants).
Frequently asked questions
Source · Generated from the editorial pipeline, verified against 3 cited references ↓
01What makes a site qualify for M85.48 versus a more specific M85.4x subcode?
02Can M85.48 be used for a solitary cyst of the jaw?
03How do I code a pathological fracture through a solitary bone cyst at an 'other site'?
04Is laterality required for M85.48?
05Does M85.48 require a 7th character extension?
06What CPT procedures are commonly linked to this diagnosis?
07Can M85.48 be reported alongside codes for osteogenesis imperfecta or polyostotic fibrous dysplasia?
Sources & references
Editorial content was developed using the following public sources. Last verified May 8, 2026.
- 01CDC ICD-10-CM Tabular List 2026
- 02icd10data.comhttps://www.icd10data.com/ICD10CM/Codes/M00-M99/M80-M85/M85-/M85.48
- 03aapc.comhttps://www.aapc.com/codes/icd-10-codes/M85.48
Mira AI Scribe
Mira's AI scribe captures the named bone affected, laterality where applicable, imaging findings (lytic lesion characteristics, MRI signal, cortical integrity), presence or absence of pathological fracture through the cyst, and any prior treatment history such as aspiration or steroid injection. This detail prevents downcoding to an unspecified bone disorder, supports medical necessity for imaging and procedural claims, and defends the 'other site' designation against audit challenge.
See how Mira captures M85.48 documentation